1. Field of the Invention
The present invention relates to a vibrating gyroscope, and more particularly, to a vibrating gyroscope that is applied to a navigation system which detects a position, or that applied to a system for damping a vibration, or the like.
2. Description of the Prior Art
A prior art of a vibrating gyroscope is disclosed in, for example, U.S. Pat. No. 5,545,822. FIG. 10 is a sectional illustrative view showing the prior art vibrating gyroscope, FIG. 11 is an exploded perspective view thereof, FIG. 12 is an exploded perspective view showing an essential portion thereof.
The vibrating gyroscope 200 shown in FIG. 10 through FIG. 12 includes a vibrator 202. The vibrator 202 includes, for example, a regular triangular prism-shaped vibrating body 204. Piezoelectric elements 206a, 206b and 206c are bonded to center portions of three side faces of the vibrating body 204, respectively. These piezoelectric elements 206a-206c respectively include piezoelectric layers consisting of, for example, ceramics, and on both surfaces of the piezoelectric layers, electrodes are respectively formed.
The vibrator 202 is supported by, for example, two U-shaped supporting members 208a and 208b. In this case, center portions of the supporting members 208a and 208b are secured to portions of one ridge-line of the vibrating body 204. Both end portions of the supporting members 208a and 208b are secured to mounting boards 210a and 210b, respectively. These mounting boards 210a and 210b are secured to one main surface of a work plate 214 via cushion members 212a and 212b. The work plate 214 is installed to one main surface of a circuit board 220 via a cushion member 216, lead terminals 218. Furthermore, a work cover 222 is engaged with the work plate 214 so as to cover the vibrator 202.
The vibrator 202 is contained in a case 224. In this case, the other cushion members 226 and 228 are provided around and over the work cover 222 in the case 224. The circuit board 220 is fixed so as to touch the case 224.
An oscillation circuit (not shown) is connected between the piezoelectric elements 206a and 206b and the piezoelectric element 206c. The oscillation circuit causes the vibrating body 204 to bend and vibrate in a direction perpendicular to the main surface of the piezoelectric element 206c. In this state, when a rotation is applied about an axis of the vibrating body 204, the vibrating direction of the vibrating body 204 is changed by the Coriolis force, thereby a difference is generated between output voltages from the piezoelectric elements 206a and 206b. Thus, by measuring the difference between the output voltages, the rotational angular velocity applied to the vibrating gyroscope can be detected.
In the vibrating gyroscope 200 shown in FIG. 10 through FIG. 12, since the cushion members 216, 226 and 228 are provided around the vibrator 202, a vibration from the outside is absorbed by these cushion members 216, 226 and 228, so that the vibration from the outside is hardly transmitted to the vibrator 202. Thus, in the vibrating gyroscope 200, the output characteristic is stable against the vibration from the outside.
However, in the vibrating gyroscope 200 shown in FIG. 10 through FIG. 12, since the vibrator 202 is supported by the circuit board 220 and the circuit board 220 touches the case 224, an impact from the outside such as a fall is applied to the vibrator 202 via the circuit board 220.
In the vibrating gyroscope 200 shown in FIG. 10 through FIG. 12, since the vibrator 202 is loosely installed to the circuit board 220 by the cushion member 216, and the lead terminals 218, when an impact is applied to the vibrator 202, a plastic strain such as twisting is easily generated between the vibrator 202 and the circuit board 220, for example, to the cushion member 216 or the lead terminals 218. When a plastic strain is generated between the vibrator 202 and the circuit board 220, the output characteristic is changed.
Thus, in the vibrating gyroscope 200 shown in FIG. 10 through FIG. 12, the output characteristic is likely to change due to an impact from the outside such as a fall.
In the vibrating gyroscope 200 shown in FIG. 10 through FIG. 12, since the work cover 222 is only engaged with the work plate 214, when a vibration or an impact is applied, the work cover 222 is likely to move or come off. In this case, the inertial force of the vibrator 202 is applied to portions where the vibrator 202 is installed on the supporting members 208a and 208b, the plasticity of the supporting members 208a and 208b is strained, and the support for the vibrator 202 becomes unstable. Consequently, a stable vibration of the vibrator 202 can not be obtained, and a good output characteristic which is sensitive to vibration can not be obtained.